Chapter 30. Introduction Single Inheritance in EJB3 Entities

The EJB specification allows you to define entities that inherit from one another. The inheritance relationships can be reflected in
queries as well. So, if you queried based on the base class, the query is polymorphic.

The tutorial example uses the single table strategy to map an inheritance relationship of org.jboss.tutorial.singleinheritance.bean.Pet,
which is the base class for org.jboss.tutorial.singleinheritance.bean.Cat and org.jboss.tutorial.singleinheritance.bean.Dog.
With the single table strategy, the entire class hierarchy is persisted in one big single table. A discriminator column is required to
differentiate between which class type is persisted in a particular row. This is what the annotations look like for Pet.

You can view the tables created by JBoss by going to the
Hypersonic Service,
scrolling down to the startDatabaseManager button and clicking it.
A Hypersonic SQL window will be minimized, but you can open it up to look at the tables and do queries.